Such devices have previously been described. The housing can be part of a flushing head. The device normally comprises a rotary table for rotatably driving the spindle. The housing can also be part of a power rotary head (also technically referred to as a “top drive”). The power rotary heads are normally arranged on a drilling rig to be displaceable in the direction of advance of the bore and comprise a driven spindle to which (optionally in segments) the drill pipe can be connected. The power rotary heads are also displaced at the same time when displacing the drill pipe during advancing or when extracting the drill pipe. In contrast, in the direction of advance, the rotary table is arranged stationary in the drilling mast. The drill pipe is movable in the longitudinal direction, but is led through in a rotationally fixed manner. The flushing heads, which serve to rotatably connect the drill pipe to the non-rotatable flushing pipe arrangement, are displaced together with the drill pipe.
Such devices normally comprise a housing with rotary lead-throughs through which the spindles are led through to the outside. In order to avoid outside contaminants from entering into the interior of the housing and lubricant, which are optionally contained in the housing, from escaping to the outside, the devices comprise rotary seal arrangements by means of which the rotary lead-throughs of the spindle through the housing can be sealed. These rotary seal arrangements consist substantially of an elastic shaft seal which acts between a first cylindrical sealing face of the spindle and, concentrically thereto, a second sealing face of the housing.
The shaft seals are subjected to high mechanical load during operation, resulting in high wear, particularly due to outside contaminants.